The present invention relates to a magnetic material sputtering target containing boron (B) which is produced via the powder sintering method, and particularly relates to a magnetic material sputtering target with minimal generation of particles during sputtering and which is useful for use in magnetic heads, magnetic resistance elements (MRAM) and the like, and to a method for producing such as a magnetic material sputtering target.
In magnetic heads and MRAMs, a tunnel magnetoresistive film having a high magnetoresistive effect is being adopted, and a magnetic body contained boron (B) is used in a material for use as the phase configuring this film. For example, known are a composition containing Co, Fe and the like and boron, Co—B, Fe—B, Co—Fe—B, or a composition obtained by adding Al, Cu, Mn, Ni or the like thereto.
In the case of Co—Fe—B, for instance, the magnetoresistive film containing B is produced by sputtering a Co—Fe—B sputtering target. This type of magnetic material target is produced via powder metallurgy or melting and casting, but in cases where a large amount of B is contained; in particular when the composition ratio of B exceeds 10 at %, a boride phase of Co or Fe with extremely brittle characteristics will be formed. Thus, when the melting method is adopted, there were problems in that the ingot would become cracked or fractured, and could not be processed into a sputtering target. While the melting method is a method that can be adopted for producing a sputtering target based on the strict management of the production process (Patent Document 1), and this method is advantageous in terms of being able to reduce oxygen and other gas components, the difficulty of the production process cannot be denied.
Meanwhile, when the sintering method is adopted, the foregoing problems that are inherent in molten products can be avoided; however, since the specific surface area of the raw material powder is great in comparison to the bulk, oxygen as a gas component is easily incorporated and the oxygen forms oxides with the metal impurities contained in the magnetic material target, and such oxides become one cause of the generation of particles during sputtering. Generally speaking, since particles deteriorate the film quality of the sputtered film and also destabilize the characteristics of magnetic heads, MRAMs and other magnetic devices, the reduction of such particles is being sought from various perspectives, and the manner of reducing particles is an extremely important issue in sputtering targets.
Note that several proposals have been made in prior patents in relation to a magnetic material target. For example, Patent Document 2 describes a Fe—Co—B-based alloy target material for depositing a soft magnetic film for use in a vertical magnetic recording medium or the like, which realizes low magnetic permeability and yields favorable sputtering characteristics. Furthermore, Patent Document 3 describes causing the atomic ratio of Fe:Co in an FeCo-based alloy to be 10:90 to 70:30, and additionally describes containing Al and/or Cr in an amount of 0.2 to 5.0 at %. Nevertheless, these Patent Documents do not focus on the impurities of the target or the particles caused by such impurities.